from The Tibetan Yogas of Dream and Sleep...

Developing the capacity for clear light dreams is similar to developing the capacity of abiding in the non-dual presence of rigpa during the day. In the beginning, rigpa and thought seem different, so that in the experience of rigpa there is no thought, and if thought arises we are distracted and lose rigpa. But when stabliity in rigpa is developed, thought simply arises and dissolves without in the least obscuring rigpa; the practitioner remains in non-dual awareness.